Feeling a little down.

I will keep this short. I just need to vent.

I have been dating girls on and off for the past 3 years....As soon as I get interested in one and they are too, they just cut me off, for no reason at all. I am nothing but nice and proper to them. I don't understand why they then goto these (excuse my verb-age, anger makes me stupid) douchebag girls who treat them like garbage and such....I'm just tired of being alone. I don't understand what I am doing wrong. Sigh. I need a hug from a cute lady.